Letrozole May Cut Risk of Breast Cancer
by: Darrin Kiessling
10/10/2003
Health officials recently halted a large international study after
an early review of the results suggested that the anti-estrogen drug
letrozole dramatically reduces the risk of recurrence of cancer among
of breast cancer survivors.
About 211,300 new cases of breast cancer are expected to be diagnosed
this year in the United States , two-thirds of them in women who have
gone through menopause. Most tumors will be estrogen-receptor positive,
meaning that the hormone fuels their growth.
The standard treatment for breast cancer is surgery, radiation and/or
chemotherapy, followed by five years of tamoxifen, which helps keep
estrogen from entering cells. Research has shown, however, that women
gain no additional benefits after they take tamoxifen for five years,
and that it may increase women's risk of endometrial cancer, pulmonary
embolism, and stroke.
The study, led by Dr. Paul Goss of Toronto 's Princess Margaret Hospital
, involved 5,187 women at hundreds of medical centers in the United
States , Canada and Europe . Half the women in the study were randomly
assigned to take letrozole. The others took placebo pills. An average
of 2.4 years after their tamoxifen treatment ended, 132 (13 percent)
women who were taking placebos developed new breast cancer or recurrences
of their original cancer, compared with 75 (7 percent) among women
taking letrozole who had a recurrence.
The study was supposed to follow the women for five years after they
had finished with tamoxifen treatments, to see if letrozole was better
than a placebo during that period. But when an independent committee
reviewed the results early, the treatment was deemed so successful
that the study was immediately halted and it was decided that all the
women taking part in the study should be given the drug.
Letrozole, made by Novartis and sold under the trade name Femara ®,
is one of a new group of anti-estrogen medications called aromatase
inhibitors. The other aromatase inhibitors currently on the market
are anastrozole, which AstraZeneca sells as Arimidex ®, and exemestane,
which Pfizer sells as Aromasin ®.
Aromatase inhibitors work by stop production of estrogen by blocking
the enzyme aromatase, which converts other hormones into estrogen.
Therefore they are not seen as entirely benign -- because these drugs
hinder estrogen production at its source, they may reduce blood levels
of estrogen by 95 percent or more. This also raises the risk of osteoporosis
and can cause hot flashes and night sweats.
The study results, along with two editorials, will
be published in the November 6, 2003, issue of The New England Journal
of Medicine, but the journal published them early on October 9 because
of their importance.
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